Soak the salt cod in cold water for 3 days until it loses most of its salt. Drain it and wash it again. Bring some water to a boil in a small pan and boil the salt cod for 3 minutes. Remove it from the water, discard the skin and save the water to cook the rice. Melt a knob or two of butter in a pan, add the chopped onion and fry gently. Add the rice and toast it for a few seconds. Pour the wine and let it evaporate then start adding the water previously saved and keep stirring. After about 10 minutes add the chopped salt cod and keep cooking. When the rice is cooked through, remove the pan from the heat, melt a knob or two of butter inside and some saffron threads. If you like, serve it with some deep fried salt cod, simply battered in flour. Deep fry for 2 minutes each side and serve it along with the rice.